Motor Mouth: How do we win the war on potholes?

Well, here’s one more thing for which we can blame global warming: Potholes.

Yes, potholes. The ruination of our roads, the deflation of many an otherwise perfectly good Michelin and the cause of more than a few scalded laps — as unfettered Timmy’s double-double meets six-inch deep crevasse — is the result of the same climate change that’s causing our glaciers to melt.

Far-fetched, you’re thinking? Not according to Susan Tighe — and she should know, seeing how she is the University of Waterloo’s Norman W. McLeod Professor in Sustainable Pavement Engineering — who says our worsening roads are the result of the rapid weather variations that greenhouse gases have wrought on our climate.

It used to be so simple. Back in the days when Canada’s seasons could be divided into nine months of (frigid) winter and three months of road construction, the deterioration of our roads was pretty straightforward. Moisture — rain, snow or whatever — would find its way under the pavement (between the top asphalt layer and its granular substrate) and freeze. Said water, now frozen, would expand, creating a bulge in the roadway. Come spring, the water would melt and disappear, leaving the bitumen to either crack or collapse. This obviously weakened the pavement and eventually that patch of asphalt would peel away, leaving — you guessed it — the aforementioned tire-puncturing, coffee-spilling pothole. The only good thing about the process was that it only happened once a year — March/April in Toronto; June/July (I only partially joke) if you lived, as I did, in Northern Quebec.

Now, says Tighe, what was once reserved for spring happens all winter long, as a result of the rapid temperature fluctuations that now plague every season. The problem, at least as it pertains to roads, is that “even in January, February and March, we now frequently see micro-climates with daytime temperatures hitting springtime levels that are then followed by a quick return to sub-zero freezing.” These rapid heating/cooling changes create the same freeze/thaw, bulge/crack/collapse cycles that used to happen primarily in spring. And though it would be an exaggeration to claim these micro-climates never occurred in winters past, it’s also true — even climate deniers don’t argue this point — that rapid temperature spikes are on the rise.

OK, so that explains how our roads are turning into motocross tracks, but why do our roads — once repaired — deteriorate so fast?

The main reason is increased traffic. While that freeze/thaw cycle is stressing our pavement from underneath, the larger number of vehicles — most especially heavy tractor-trailers and busses — is pounding it from above. The problem is that while they appears rigid, our roads are actually designed to be quite flexible — “viscoelastic,” as Tighe calls it — and they bend/distort much more under the impact of one heavily-loaded tractor-trailer tire (possibly 10,000 times as much!) than a whole bunch of comparatively lightly-loaded car tires.

And, while many of the problems are simply physical — and their solutions, thicker pavement can withstand heavier loading, well known — one of the biggest issues affecting the long-term health of our roads is plain old human indulgence. According to Tighe, our unwillingness to be inconvenienced greatly affects the quality of our roads. “The public needs to be open to closing roads for regular maintenance” in order for work crews to provide proper repair. But since completely closing down major highways and arterial urban streets is often unthinkable — or at least politically inexpedient — compromises are made. One of the reasons that repairs to Toronto’s Don Valley Parkway are done right is that the entire thoroughfare is often closed for 24 to 48 hours for crews to effectively complete repairs.

The good news is that, if we are part of the problem, moving forward we may also be part of the solution. As it turns out, one of the biggest problems is — believe it or not — that repair crews don’t know where the potholes are. That’s ridiculous, I can already hear you screaming, the damnable road conditions you see every day seemingly obvious to anyone.

But that’s just the point; you see them every day. Municipalities, or the civil engineering firms they hire, have to identify and quantify each and every crack and crevasse to prioritize them for repair. According to John Zelek, co-director of the Vision/Image Processing Lab at Waterloo, that’s accomplished either by (in affluent communities) camera-equipped cars or, in smaller cities, by literally driving around with pen and paper, noting, by hand, where the bumps are. Either way, it takes months and the information is already dated by the time the study is finished.

A better solution, says Zelek to equip civic vehicles — police cars, fire trucks, etc. — with cameras and then feed their imagery to computers that can categorize the road damage automatically. Even better, some luxury cars — like any Mercedes-Benz equipped with the company’s Magic Body Control system — already use cameras to spot bumps in the road ahead and the (semi-) autonomous future we’re all told is right around the corner also requires visual sensors in every car. It’s not an exaggeration to say we may soon be able to crowd-source — Waze-style — the entire pothole detection process.

It could get even simpler, claims Zakariya Gadi, a Concordia University civil engineering masters student, who developed a pothole detection system earlier this year that uses nothing more exotic than a common, everyday smartphone — Gadi used a creeky old Galaxy S4 in his testing. Now Measuring the Impacts of Climatic Exposure to Pavement Deterioration with Low Cost Technology may sound about as boring as an Andrew Scheer speech, but considering that we spend $12 billion each and every year maintaining our roads, Gadi’s Samsung could be a real tax saver.

Of course, none of those are nearly as high-tech as a Transformer-like machine that automatically repairs 50 potholes a day without the need for even one manual labourer, or the Dutch engineer who claims to have invented a road that repairs itself. But, a) they are not fantasies of a distant future and, more importantly, b) they are home-grown solutions to a uniquely Canadian problem.

We may win the war on the potholes yet.

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